Various processes for producing aldehyde and/or alcohol compounds by the reaction of an olefin with carbon monoxide and hydrogen in the presence of a catalyst are known. Typically, these reactions are performed at elevated temperatures and pressures. The aldehyde and alcohol compounds that are produced generally correspond to compounds obtained by the addition of a carbonyl or carbinol group, respectively, to an unsaturated carbon atom in the starting material with simultaneous saturation of the unsaturated carbon-carbon bond. Isomerization of the olefin bond may take place to varying degrees under certain conditions; thus, as a consequence of this isomerization, a variety of products may be obtained. These processes are typically known as hydroformylation reactions.
The catalyst employed in a hydroformylation reaction typically comprises a transition metal, such as cobalt, platinum, rhodium or ruthenium, in complex combination with carbon monoxide and ligand(s) such as an organophosphine.
The following documents are representative of the earlier hydroformylation methods which use transition metal catalysts: U.S. Pat. No. 3,420,898, U.S. Pat. No. 3,501,515, U.S. Pat. No. 3,448,157, U.S. Pat. No. 3,440,291, U.S. Pat. No. 3,369,050 and U.S. Pat. No. 3,448,158.
As mentioned above, several products may be obtained. In case of for instance the hydroformylation of propylene, a mixture of normal butyraldehyde and iso-butyraldehyde may be formed, which through a subsequent hydrogenation may be converted to a mixture of normal butyl-alcohol and isobutyl-alcohol. In attempts to improve the selectively of the hydroformylation reaction toward either normal butyraldehyde and iso-butyraldehyde, attention has typically focussed on developing novel catalysts and novel processes for recovering and re-using the catalyst. In particular, novel catalysts have been developed which may exhibit improved selectively toward normal butyraldehyde and optionally normal butyl-alcohol. In WO 2011/087690 A1 a hydroformylation process is described using a rhodium based catalyst comprising at least two different ligand molecules. According to WO 2011/087690 A1 the use of the two different ligand molecules may provide a higher normal butyraldehyde over iso-butyraldehyde ratio.
A disadvantage of the process of WO 2011/087690 A1 is that it requires two different ligand molecules, which makes the catalyst system and accompanying process complex and expensive.
There is a need for a process to produce aldehydes and/or alcohols at a high normal over iso-aldehydes or alcohol ratio or a high iso over normal aldehydes or alcohol ratio, without the need to use complex hydroformylation catalyst(s).